Method and apparatus for determining transport block size

ABSTRACT

In the field of wireless communication technologies, method and apparatus for determining a transport block size (TBS) of a data channel are provided. In a communication network, a terminal device receives control information from a network device. The control information includes modulation indication information and resource information of the data channel. The terminal device determines a modulation order and a code rate according to the modulation indication information, and determines number of time-frequency resources according to the resource indication information of the data channel. The terminal device determines the TBS according to the modulation order, the code rate, and the number of time-frequency resources. Based on the determined TBS, the terminal device decodes the data channel carried on the time-frequency resources or sends the data channel on the time-frequency resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/091692, filed on Jun. 15, 2018, which claims priority toChinese Patent Application No. 201710459621.X, filed on Jun. 16, 2017,and Chinese Patent Application No. 201710686578.0, filed on Aug. 11,2017. The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the field of communication technologies, andin particular, to method and apparatus for determining a transport blocksize (TBS).

BACKGROUND

Fifth Generation (5G) wireless communication systems (also referred toas new radio (NR) wireless communication systems) are purpose-built tosupport improved system performance. The 5G communication systemssupport a plurality of service types, a plurality of deploymentscenarios, and wider spectrum ranges. The 5G wireless communicationsystems need to support different requirements from services ofdifferent service types. Therefore, resource scheduling in the 5Gsystems needs to have greater flexibility, and determination of atransport block size (TBS) in the resource scheduling needs to be moreflexible.

In existing fourth generation (4G) Long Term Evolution (LTE) systems,for example, the determination of a TBS on a data channel of a terminaldevice includes the following steps:

Step 1: The terminal device determines a modulation scheme (modulationorder) and a TBS index (I_TBS) according to a modulation and codingscheme (MCS) index (I_MCS) and an MCS mapping table predefined in aprotocol.

Step 2: The terminal device determines, according to resource allocationinformation indicated by a network device, number of physical resourceblocks (number of PRB, N_PRB) allocated in frequency domain.

Step 3: The terminal device searches in a predefined TBS table for acorresponding TBS value based on parameters such as the I_TBS and theN_PRB, to determine the TBS carried on the data channel.

In LTE systems, a basic assumption for determining the TBS is that abasic time unit for resource scheduling is one subframe (i.e. 14orthogonal frequency division multiplexing (OFDM) symbols), and thatnumber of resource elements available to the data channel in each PRB isfixed, for example, 120 resource elements (RE). However, for the 5Gwireless communication systems, flexibility of resource schedulingincreases greatly, and number of resource elements available to the datachannel in each PRB varies greatly. In addition, scheduling time rangesand frequency domain ranges to be supported by the 5G wirelesscommunication systems are extremely large. Therefore, if still using amanner of determining the TBS on the data channel in the LTE systems,operations would not be flexible, and scalability would be poor.

SUMMARY

Embodiments of this application provide a method for determining atransport block size, and an apparatus, to improve flexibility of amanner of determining a transport block size.

According to a first aspect, a method for determining a transport blocksize is provided, and the method includes: receiving, by a terminaldevice, control information sent by a network device, where the controlinformation includes indication information and resource information ofa data channel; determining, by the terminal device, a modulation schemeand a code rate based on a first mapping relationship set and theindication information, and determining number of time-frequencyresources based on the resource information of the data channel, wherethe first mapping relationship set includes a correspondence between theindication information and a combination of the modulation scheme andthe code rate; determining, by the terminal device, a first transportblock size (TBS) based on the modulation scheme, the code rate, and thenumber of time-frequency resources; and decoding, by the terminal devicebased on the first TBS, the data channel carried on the time-frequencyresources, or sending, by the terminal device on the time-frequencyresources, the data channel based on the first TBS.

According to a second aspect, a method for determining a transport blocksize is provided, and the method may include:

determining, by a network device, a modulation scheme and a code rate,and determining indication information based on a first mappingrelationship set and a combination of the modulation scheme and the coderate, where the first mapping relationship set includes a correspondencebetween the indication information and the combination of the modulationscheme and the code rate;

sending, by the network device, control information to a terminaldevice, where the control information includes the indicationinformation and resource information of a data channel, and the resourceinformation is used to determine number of time-frequency resources;

determining, by the network device, a first transport block size (TBS)based on the modulation scheme, the code rate, and the number oftime-frequency resources; and

decoding, by the network device based on the first TBS, the data channelcarried on the time-frequency resources, or sending, by the networkdevice on the time-frequency resources, the data channel based on thefirst TBS.

In the embodiments of this application, the terminal device maydetermine the modulation scheme and the code rate from the first mappingrelationship set based on the control information delivered by thenetwork device, and may further determine the number of time-frequencyresources based on the control information. The time-frequency resourcesare time-frequency resources for sending or receiving the data channel,to be specific, time-frequency resources actually occupied by the datachannel. Further, the terminal device may determine the TBS on the datachannel. In this way, the TBS determined based on the time-frequencyresources actually occupied by the data channel more matches a targetcode rate of the data channel, thereby improving accuracy of the TBS.The target code rate herein is a code rate that the network deviceexpects the data channel to reach, and the foregoing code rate is a coderate actually used by the data channel.

In addition, because the TBS is determined based on the modulationscheme, the code rate, and the number of time-frequency resources, arelatively accurate TBS can be determined in a same manner regardless ofnumber of scheduled resources and regardless of number of other overheadresources in the scheduled resources. Therefore, the manner ofdetermining a TBS is applicable to various scheduling scenarios, and themanner of determining a TBS is highly flexible and has good scalability.

Further, because the determined TBS is more accurate, number oftime-frequency resources allocated to the terminal device is notextremely small, so that a retransmission possibility can be reducedwhen sending the data channel or receiving the data channel, and thenumber of time-frequency resources allocated to the terminal device isnot excessively large either, thereby avoiding resource waste.

Optionally, the determining, by the terminal device or the networkdevice, a first transport block size (TBS) based on the modulationscheme, the code rate, and the number of time-frequency resourcesincludes:

determining, by the terminal device or the network device, the first TBSbased on the modulation scheme, the code rate, the number oftime-frequency resources, and number of transport layers, where

the first TBS meets the following formula:

${{{First}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is the number of time-frequency resources, v is the number oftransport layers that is supported by the data channel, Q is amodulation order corresponding to the modulation scheme, and R is thecode rate.

N may be quantized with a large granularity, and

${N = {K \times \left\lceil \frac{N\_ TEMP}{K} \right\rceil}},$K is a positive integer, where

N_TEMP may be number of time-frequency resources available to the datachannel, N is quantized number of time-frequency resources available tothe data channel, and N is used to calculate the first TBS and/or asecond TBS. Details are not described below.

Optionally, the first TBS may be obtained by looking up a table based onthe number N of time-frequency resources available to the data channel,the number v of transport layers that is supported by the data channel,and the modulation scheme.

Optionally, number L of bits carried on a unit resource may be obtainedby looking up a table based on the modulation scheme and the number v oftransport layers that is supported by the data channel, and further, thefirst TBS is obtained by multiplying the number L of bits carried on theunit resource and a ratio of the number N of time-frequency resourcesavailable to the data channel to number of resources included in theunit resource.

Optionally, number L of bits carried in single layer transmission may beobtained by looking up a table based on the number N of time-frequencyresources available to the data channel and the modulation scheme, andfurther, the first TBS is obtained by multiplying the number L of bitscarried in single layer transmission and the number v of transportlayers that is supported by the data channel.

Optionally, number L of bits carried in single layer transmission on aunit resource may be obtained by looking up a table based on themodulation scheme, and further, the first TBS is obtained by multiplyingthe number L of bits carried in single layer transmission on the unitresource, a ratio of the number N of time-frequency resources availableto the data channel to number of resources included in the unitresource, and the number v of transport layers that is supported by thedata channel.

In the embodiments of this application, the TBS may be determinedthrough calculation by using a formula with reference to parameters suchas the modulation scheme, the code rate, the number of time-frequencyresources, and the number of transport layers that is supported by thedata channel, so that efficiency in determining the TBS is higher.Further, in this application, the TBS may be determined in other mannersthan a manner of looking up a table. Therefore, there is no need todesign a TBS table, implementation complexity of determining the TBS isreduced, and applicability is better. Certainly, in the embodiments ofthis application, a corresponding TBS table may be designed based on theforegoing formula, but a value obtained by looking up the table meetsthe foregoing formula. In this way, accuracy of the TBS can also beimproved.

Optionally, the terminal device or the network device may determine asecond TBS based on the modulation scheme, the code rate, the number oftime-frequency resources, and number of transport layers, and determinethe first TBS based on the second TBS.

The first TBS meets the following condition: when the second TBS isgreater than a first reference threshold, the first TBS is equal to thesecond TBS.

In the embodiments of this application, the second TBS is introducedbefore the final first TBS is determined.

Optionally, the terminal device or the network device may determine thesecond TBS based on the modulation scheme, the code rate, the number oftime-frequency resources, and the number of transport layers; and

the second TBS meets the following formula:

${{{Second}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is the number of time-frequency resources, v is the number oftransport layers that is supported by the data channel, Q is amodulation order corresponding to the modulation scheme, and R is thecode rate.

Optionally, the second TBS may be obtained by looking up a table basedon number N of time-frequency resources available to the data channel,the number v of transport layers that is supported by the data channel,and the modulation scheme.

Optionally, number L of bits carried on a unit resource may be obtainedby looking up a table based on the modulation scheme and the number v oftransport layers that is supported by the data channel, and further, thesecond TBS is obtained by multiplying the number L of bits carried onthe unit resource and a ratio of number N of time-frequency resourcesavailable to the data channel to number of resources included in theunit resource.

Optionally, number L of bits carried in single layer transmission may beobtained by looking up a table based on number N of time-frequencyresources available to the data channel and the modulation scheme, andfurther, the second TBS is obtained by multiplying the number L of bitscarried in single layer transmission and the number v of transportlayers that is supported by the data channel.

Optionally, number L of bits carried in single layer transmission on aunit resource may be obtained by looking up a table based on themodulation scheme, and further, the second TBS is obtained bymultiplying the number L of bits carried in single layer transmission onthe unit resource, a ratio of number N of time-frequency resourcesavailable to the data channel to number of resources included in theunit resource, and the number v of transport layers that is supported bythe data channel.

In the embodiments of this application, the terminal device or thenetwork device obtains the second TBS based on parameters such as themodulation scheme, the code rate, the number of time-frequencyresources, and the number of transport layers, and then compares thesecond TBS with the first reference threshold. If the second TBS isgreater than the first reference threshold, the second TBS may be usedas a finally required TBS, namely, the first TBS. Optionally, in theembodiments of this application, if the second TBS obtained throughcalculation is less than or equal to the first reference threshold, anelement (a first element) in a first value set may be determined as afinally required TBS, namely, the first TBS.

In the embodiments of this application, according to a manner ofdetermining the first TBS by comparing the second TBS with the firstreference threshold, transmission of a small data packet (or referred toas a small-sized packet), especially transmission of a special datapacket, is more efficient, and a manner of determining a TBS when alarge data packet is transmitted is more flexible, more applicable, andwith better scalability. The special data packet may include a Voiceover Internet Protocol (VoIP) packet, a Medium Access Control (MAC)control element (CE) packet, an enhanced voice services (EVS) codec (EVScodec) packet, and the like.

Optionally, the first reference threshold is greater than or equal to asize of a maximum VoIP packet or a size of a maximum MAC CE packet.

Optionally, the first value set includes at least one of a size of aVoIP packet and/or a size of a MAC CE packet.

Optionally, the first value set includes at least one of the followingvalues: 8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 136, 144, 152, 176,208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408, 424, 440,456, 472, 488, 504, 520, and 536.

Optionally, the first element is an element that is in the first valueset and that is less than or equal to the second TBS, and an absolutevalue of a difference between the element and the second TBS is thesmallest; or

the first element is an element that is in the first value set and thatis greater than or equal to the second TBS, and an absolute value of adifference between the element and the second TBS is the smallest; or

the first element is an element in the first value set, and an absolutevalue of a difference between the element and the second TBS is thesmallest.

In the embodiments of this application, a value set is defined based onthe size of the VoIP packet or the size of the MAC CE packet. An elementincluded in the value set may be the size of the VoIP packet, or may bethe size of the MAC CE packet. Optionally, in the embodiments of thisapplication, some values may be directly provided, and these values arerepresented by using an array or a set, to obtain a value set. The datamay be a size of an existing VoIP packet or a size of an existing MAC CEpacket, or may be a size of an extended VoIP packet or a size of anextended MAC CE packet, or may be some other inserted values than avalue of the size of the VoIP packet and a value of the size of the MACCE packet. In the embodiments of this application, the first referencethreshold is set based on the size of the VoIP packet or the size of theMAC CE packet, and according to the determining manner of determiningthe first TBS by comparing the first reference threshold and the secondTBS, transmission of the small-sized packet, especially transmission ofthe special data packet, is more efficient, and the manner ofdetermining a TBS when a large packet is transmitted is more flexibleand more applicable. If the second TBS is less than or equal to the sizeof the maximum VoIP packet or the size of the maximum MAC CE packet, anelement in the first value set may be selected as the first TBS, so thattransmission of the small-sized packet, especially transmission of thespecial data packet, is more efficient. If the second TBS is greaterthan the size of the maximum VoIP packet or the size of the maximum MACCE packet, the second TBS is determined as the first TBS, so that themanner of determining a TBS when a large packet is transmitted is moreflexible, more applicable, and with better scalability.

Optionally, the terminal device or the network device may determine asecond TBS based on the modulation scheme, the code rate, the number oftime-frequency resources, and number of transport layers, and determinethe first TBS based on the second TBS.

The first TBS meets the following condition:

when an absolute value of a difference between the second TBS and asecond element in a first value set is less than or equal to a secondreference threshold, the first TBS is the second element in the firstvalue set.

Alternatively, feasibly, when an absolute value of a difference betweenthe second TBS and a second element in a first value set is greater thana second reference threshold, the first TBS is equal to the second TBS.

Optionally, the second reference threshold is a predefined value, or thesecond reference threshold is a product value of the second element anda predefined coefficient.

In the embodiments of this application, after the second TBS isobtained, differences between the second TBS and elements included inthe first value set are calculated one by one, absolute values of thedifferences obtained through calculation are compared with the secondreference threshold in sequence, and one element in the first value setis determined as the first TBS based on a comparison result. Optionally,in the embodiments of this application, it may be defined that a mannerof determining the first TBS includes a manner 1 and a manner 2. In themanner 1, when the absolute value of the difference between the secondTBS and the second element in the first value set is greater than thesecond reference threshold, the second TBS may be determined as thefirst TBS, so that a manner of determining a TBS when a large datapacket is transmitted is more flexible, more applicable, and with betterscalability. In the manner 2, an element (the second element) in thefirst value set is determined as the first TBS, where an absolute valueof a difference between the element and the second TBS is less than orequal to the second reference threshold, so that transmission of a smalldata packet (or referred to as a small-sized packet), especiallytransmission of a special data packet, is more efficient.

Optionally, the resource information indicates time-frequency resourcesallocated by the network device to the terminal device, and the numberof time-frequency resources is number of remaining time-frequencyresources obtained after a specified time-frequency resource issubtracted from the time-frequency resources indicated by the resourceinformation.

Correspondingly, the determining number of time-frequency resourcesbased on the resource information of the data channel includes:

determining, by the terminal device, the number of time-frequencyresources based on the resource information and the specifiedtime-frequency resource, where the time-frequency resources include theremaining time-frequency resources obtained after the specifiedtime-frequency resource is subtracted from the time-frequency resourcesindicated by the resource information.

The specified time-frequency resource may include one or more of atime-frequency resource occupied by a demodulation reference signal(DMRS) corresponding to the data channel, a time-frequency resourceoccupied by a channel state information-reference signal (CSI-RS) sentby the network device on the time-frequency resources indicated by theresource information, and a time-frequency resource reserved by thenetwork device.

Optionally, the time-frequency resource reserved by the network devicemay include a time-frequency resource occupied by a signal or a channelpreconfigured by the network device, for example, a time-frequencyresource occupied by a primary synchronization signal (PSS), a secondarysynchronization signal (SSS), a physical broadcast channel (PBCH), orthe like.

In the embodiments of this application, the resource information of thedata channel may be indicated by using the control information, and theterminal device determines, based on the time-frequency resourcesindicated by the resource information and a fixed overheadtime-frequency resource, the time-frequency resources available to thedata channel, so that a manner of determining the number oftime-frequency resources available to the data channel is more flexible,and the determined number of time-frequency resources is more accurate,thereby improving accuracy of the determined TBS.

Optionally, the first mapping relationship set is a default mappingrelationship set in a plurality of mapping relationship sets.

Alternatively, before the receiving, by a terminal device, controlinformation sent by a network device, the method further includes:receiving, by the terminal device, configuration information sent by thenetwork device. Alternatively, before the sending, by the networkdevice, control information to a terminal device, the method furtherincludes: sending, by the network device, configuration information tothe terminal device. The configuration information indicates the firstmapping relationship set, and the first mapping relationship set is oneof a plurality of mapping relationship sets.

Optionally, one mapping relationship set may correspond to one table.Each mapping relationship set may include one or more combinations ofmodulation schemes and code rates, and each combination may correspondto one piece of indication information. Further, the indicationinformation may be an index.

In the embodiments of this application, a plurality of mappingrelationship sets may be configured or defined, and each mappingrelationship set may be applicable to a service of the terminal device.In this way, the terminal device or the network device may selectdifferent mapping relationship tables based on different services, tobetter adapt to the service of the terminal device. It should be notedthat the plurality of mapping relationship sets are not only related toservices, but also may be related to other information. This is notlimited in this application. In this way, when using a plurality ofmapping relationship sets, the terminal device or the network device maydetermine a mapping relationship set based on other information, orselect a default mapping relationship set.

Optionally, the control information further includes mappingrelationship set indication information, the mapping relationship setindication information indicates the first mapping relationship set, andthe first mapping relationship set is one of a plurality of mappingrelationship sets.

Optionally, a format of the control information indicates the firstmapping relationship set, and the first mapping relationship set is oneof a plurality of mapping relationship sets.

Optionally, a type of information carried on the data channel indicatedby the control information indicates the first mapping relationship set,and the first mapping relationship set is one of a plurality of mappingrelationship sets.

In the embodiments of this application, a mapping relationship setapplicable to the terminal device may be indicated by using the controlinformation or the configuration information. This may dynamically adaptto a plurality of flexible resource allocation scenarios, andapplicability is better.

Optionally, the control information includes precoding indicationinformation, and the precoding indication information indicates thenumber of transport layers that is supported by the data channel.Correspondingly, before the determining, by the terminal device, a firsttransport block size (TBS) based on the modulation scheme, the coderate, and the number of time-frequency resources, the method furtherincludes: determining, by the terminal device based on the precodingindication information included in the control information, the numberof transport layers that is supported by the data channel.

Optionally, before the determining, by the terminal device, a firsttransport block size (TBS) based on the modulation scheme, the coderate, and the number of time-frequency resources, the method furtherincludes:

determining, by the terminal device based on a transmission modecorresponding to the data channel, the number of transport layers thatis supported by the data channel.

Correspondingly, before the determining, by the network device, a firsttransport block size (TBS) based on the modulation scheme, the coderate, and the number of time-frequency resources, the method furtherincludes: determining, by the network device based on a transmissionmode corresponding to the data channel, the number of transport layersthat is supported by the data channel.

In the embodiments of this application, the number of transport layersthat is supported by the data channel may be determined in a pluralityof manners, and a manner of determining the number of transport layersthat is supported by the data channel is more flexible. This may betteradapt to various resource allocation scenarios.

According to a third aspect, a terminal device is provided, and theterminal device may include a transceiver unit and a processing unit.The transceiver unit and the processing unit may perform functions ofthe terminal device in the first aspect and the foregoing optionalimplementations.

According to a fourth aspect, a network device is provided, and thenetwork device may include a transceiver unit and a processing unit. Thetransceiver unit and the processing unit may perform functions of thenetwork device in the second aspect and the foregoing optionalimplementations.

According to a fifth aspect, a terminal device is provided, and theterminal device may include a processor, a memory, and a transceiver,where

the memory and the transceiver are connected to the processor;

the memory is configured to store a group of program code; and

the processor and the transceiver are configured to invoke the programcode stored in the memory, to perform the method provided in the firstaspect.

According to a sixth aspect, a network device is provided, and thenetwork device may include a processor, a memory, and a transceiver,where

the memory and the transceiver are connected to the processor;

the memory is configured to store a group of program code; and

the processor and the transceiver are configured to invoke the programcode stored in the memory, to perform the method provided in the secondaspect.

According to a seventh aspect, a communications system is provided, andthe system includes the terminal device provided in the third aspect andthe network device provided in the fourth aspect.

According to an eighth aspect, a computer storage medium is provided,the computer storage medium is configured to store a computer softwareinstruction used by the foregoing terminal device, and the computersoftware instruction includes a program designed to perform theforegoing aspects.

According to a ninth aspect, a computer storage medium is provided, thecomputer storage medium is configured to store a computer softwareinstruction used by the foregoing network device, and the computersoftware instruction includes a program designed to perform theforegoing aspects.

According to a tenth aspect, a chip is provided, and the chip is coupledto a transceiver in a network device, to perform the technical solutionin the second aspect of the embodiments of this application. It shouldbe understood that “couple” in this embodiment of this applicationindicates a direct connection or an indirect connection between twoparts. The connection may be fixed or movable, and the connection mayallow communication of a fluid, electricity, an electrical signal, oranother type of signal between the two parts.

According to an eleventh aspect, a chip is provided, and the chip iscoupled to a transceiver in a terminal device, to perform the technicalsolution in the first aspect of the embodiments of this application. Itshould be understood that “couple” in this embodiment of thisapplication indicates a direct connection or an indirect combinationbetween two parts. The connection may be fixed or movable, and theconnection may allow communication of a fluid, electricity, anelectrical signal, or another type of signal between the two parts.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic architectural diagram of a communication system;

FIG. 2 is a schematic diagram of a method for determining a transportblock size according to an embodiment of this application;

FIG. 3 is a schematic block diagram of a terminal device according to anembodiment of this application;

FIG. 4 is a schematic block diagram of a network device according to anembodiment of this application; and

FIG. 5 is a schematic structural diagram of a communication deviceaccording to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

The following describes the embodiments of this application withreference to the accompanying drawings.

The method and apparatus for determining a transport block size, thatare provided in the embodiments of this application, may be applicableto an LTE system, a 5G communication system, or other wirelesscommunication systems that use various radio access technologies. Forexample, the method and apparatus for determining a transport block sizemay be applicable to communication systems that use access technologieslike Code Division Multiple Access (CDMA), Frequency Division MultipleAccess (FDMA), Time Division Multiple Access (TDMA), orthogonalfrequency division multiple access (OFDMA), and single carrier frequencydivision multiple access (SC-FDMA). The following gives a description ofthe embodiments by using the 5G communication system as an example.

FIG. 1 shows a basic architecture of a communication system. Thecommunication system may include a network device, a terminal device,and the like. The network device and the terminal device may performdata or signaling transmission by using a wireless interface, and thetransmission includes uplink transmission and downlink transmission.

The terminal device is a device that has wireless transmission/receptionfunctions. The terminal device may be deployed on land as, for example,an indoor device, an outdoor device, a handheld device, or an in-vehicledevice. The terminal device may also be deployed on the water (forexample, on a ship), or may also be deployed in the air (for example, ona plane, a balloon, or a satellite). The terminal device may be a mobilephone, a tablet computer, a computer having a wirelesstransmission/reception functions, a virtual reality (VR) terminaldevice, or an augmented reality (AR) terminal device. The terminaldevice may be used as a wireless terminal in industrial control, awireless terminal in self driving, a wireless terminal in telemedicine(remote medical), a wireless terminal in a smart grid, a wirelessterminal in transportation safety, a wireless terminal in a smart city,a wireless terminal in a smart home, or the like.

For ease of description, in subsequent descriptions of the embodimentsof this application, the devices mentioned above are collectivelyreferred to as a terminal device.

The network device referred to in embodiments of this application is anapparatus that is deployed in a radio access network (RAN) and that isconfigured to provide wireless communication functions for the terminaldevice. The network device may be specifically a base station, and maybe in various forms such as a macro base station, a micro base station,a relay node, an access point base station controller, a transmissionreception point (TRP), and the like. The base station may have differentspecific names in systems that use different radio access technologies.For example, in an LTE network, the base station is referred to as anevolved NodeB (eNB), and in subsequent evolved systems, the base stationmay be referred to as a new radio nodeB or next generation nodeB (gNB).For ease of description, in subsequent descriptions of the embodimentsof this application, the devices mentioned above are collectivelyreferred to as a network device.

The 5G communication systems are purpose-built to support improvedsystem performance. The 5G communication systems support a plurality ofservice types, different deployment scenarios, and wider spectrumranges. The plurality of service types include enhanced mobile broadband(eMBB), massive machine type communication (mMTC), ultra-reliable andlow latency communications (URLLC), multimedia broadcast multicastservice (MBMS), positioning service, and the like. The differentdeployment scenarios may include indoor hotspot, dense urban area,suburbs, urban macro, and high-speed railway scenarios. The widerspectrum ranges means that the 5G wireless communication systems willsupport spectrum ranges up to 100 gigahertz (GHz), and the spectrumranges include a low-frequency part of less than 6 GHz, and ahigh-frequency part ranging from 6 GHz to 100 GHz.

Compared with communication systems using the fourth generation (4G)mobile communication technologies, a feature of the 5G communicationsystems is the support for URLLC. URLLC includes a plurality of servicetypes. Typical application cases include industrial control, automationof industrial production process, human-computer interaction,telemedicine, and the like. To better quantify performance indicators ofa URLLC service, so as to provide reference inputs and evaluationcriteria for a design of a 5G communication system, a RAN working groupand a RAN1 working group of the 3rd Generation Partnership Project(3GPP) define performance indicators (including delay, reliability,system capacity, and the like) of the URLLC service as follows:

Delay: A delay is a transmission time for a user application layer datapacket from a service data unit (SDU) of a radio protocol layer 2 and/ora radio protocol layer 3 at a transmit end to an SDU of a radio protocollayer 2 and/or a radio protocol layer 3 at a receive end. A user planedelay requirement of the URLLC service is 0.5 millisecond (ms) for bothuplink and downlink transmissions. The delay requirement is onlyapplicable to a scenario in which a network device and a terminal deviceare not in a discontinuous reception (DRX) state. The performancerequirement of 0.5 ms is an average delay of the data packet, and is notbound to reliability requirement in the performance indicators of theURLLC service.

Reliability: Reliability is a success probability of correctlytransmitting a certain amount (assumed to be X bits) of data within aspecific transmission time (assumed to be L seconds) in a datatransmission process from a transmit end to a receive end at a certainchannel quality. The transmission time is still defined as atransmission time required for a user application layer data packet froman SDU of a radio protocol layer 2 and/or a radio protocol layer 3 atthe transmit end to an SDU of a radio protocol layer 2 and/or a radioprotocol layer 3 at the receive end. For the URLLC service, a typicalrequirement is to achieve reliability of 99.999% within 1 ms. It shouldbe noted that the foregoing performance indicator is merely a typicalvalue. In specific implementations, URLLC services in differentapplication scenarios may have different reliability requirements. Forexample, in some extremely stringent industrial control services, it isrequired that a delay from a transmit end to a receive end is within0.25 ms and that reliability of data transmission reaches 99.9999999%.

System capacity: A system capacity is a maximum throughput of a cellthat the system can achieve on the premise of having a specificproportion of interrupted users. An interrupted user is a user whosereliability requirement the system cannot meet in a specific delayrange. In other words, reliability that is required by some users in aspecific delay range cannot be met by the system, and the users arereferred to as interrupted users.

The 5G communication systems need to support requirements of differentperformance indicators of a plurality of services. Therefore, resourcescheduling of the 5G communication systems need to be more flexible. Amore flexible resource scheduling manner means a more flexible datatransmission. Therefore, a manner of determining a transport block size(TBS) in data transmission also needs to be more flexible. Theembodiments of this application provide a method and an apparatus fordetermining a TBS. The method and the apparatus allow for a moreflexible resource scheduling manner, and meet requirements for morediversified service performance indicators.

With reference to FIG. 2 to FIG. 5, the following describes the methodand the apparatus for determining a TBS according to the embodiments ofthis application.

FIG. 2 is a schematic diagram of a method for determining a TBSaccording to an embodiment of this application. The method provided inthis embodiment of this application includes the following steps.

S20. A network device determines a modulation scheme and a code rate,and determines indication information based on a first mappingrelationship set and a combination of the modulation scheme and the coderate.

In a 5G communication system, a terminal device may support one or moreservices, for example, a URLLC service, an eMBB service, and an mMTCservice.

In a specific implementation, one service supported by the terminaldevice may correspond to one mapping relationship set. A typical mappingrelationship set may be represented as one table such as the followingTable 1 or Table 2. Table 1 is a schematic table of a mappingrelationship set of a modulation scheme and a code rate. For ease ofdescription, the mapping relationship set shown in Table 1 may be set toa mapping relationship set 1 in a subsequent description of thisembodiment of this application. Table 2 is another schematic table of amapping relationship set of a modulation scheme and a code rate. Forease of description, the mapping relationship set shown in Table 2 maybe set to a mapping relationship set 2 in a subsequent description ofthis embodiment of this application.

Optionally, each mapping relationship set may include one or morecombinations of modulation schemes and code rates, and each combinationmay correspond to one piece of indication information. For example,combinations of modulation schemes and code rates in Table 1 include acombination (set to a combination 1) of a modulation scheme quadraturephase shift keying (QPSK) (corresponding to a modulation order 2) and acode rate 0.01, and indication information corresponding to thecombination 1 is an MCS index that is equal to 0.

Optionally, the mapping relationship set may also be represented inother forms than a table, and may be specifically determined based on anactual application scenario requirement. This is not limited herein.

TABLE 1 Modulation and Coding Scheme Modulation scheme (which may beIndex (MCS index) represented by a modulation order) Code Rate 0 2 0.011 2 0.03 2 2 0.05 3 2 0.07 4 2 0.09 5 4 0.11 6 4 0.13 7 4 0.15

As shown in the foregoing Table 1, for the modulation schemes and thecode rates shown in the mapping relationship set 1, there are eightcombinations of the modulation schemes and the code rates of a datachannel, and the modulation schemes include quadrature phase shiftkeying (QPSK) and 16 quadrature amplitude modulation (16QAM). Onemodulation scheme corresponds to one modulation order. Therefore, acorrespondence between a modulation scheme and a code rate may bespecifically represented by using a correspondence between a modulationorder and a code rate. For example, a modulation order (denoted as Q orQ_(m)) of the modulation scheme QPSK is 2, and a modulation order of amodulation scheme 16QAM is 4. In a specific implementation, themodulation scheme may also be represented in another data form. This isnot limited herein.

The code rates of the data channel are concentrated in a low code ratearea, for example, a low code rate area ranging from 0.01 to 0.15. Forexample, because the URLLC service has performance requirements of highreliability and low delay, modulation schemes of the URLLC service aremainly lower-order modulation schemes, and code rates are mainlyconcentrated in a low code rate range. Therefore, the mappingrelationship set 1 may be applicable to the URLLC service and the likesupported by the terminal device. The URLLC service is merely anexample. The mapping relationship set 1 may also be applicable to moretypes of services, and an applicable service type may be specificallydetermined based on an actual application scenario. This is not limitedherein.

As shown in the foregoing Table 1, one combination of a modulationscheme and a code rate may correspond to one index. The index of themodulation scheme and the code rate may be an MCS index, or may be indexinformation in another representation form. This is not limited herein.For ease of description, the following uses the MCS index to give adescription, and details are not described in Table 2.

TABLE 2 Modulation and Coding Scheme Index (MCS index) Modulation OrderCode Rate 0 2 0.05 1 2 0.1 2 2 0.15 3 2 0.2 4 2 0.25 5 4 0.3 6 4 0.35 74 0.4 8 4 0.45 9 4 0.5 10 4 0.55 11 6 0.6 12 6 0.65 13 6 0.7 14 6 0.7515 6 0.8

As shown in the foregoing Table 2, for modulation schemes and code ratesshown in the mapping relationship set 2, there are 16 combinations ofthe modulation schemes and the code rates of a data channel. Themodulation schemes include QPSK (a corresponding modulation order is 2,and to be specific, Q=2 or Q_(m)=2), 16QAM (a corresponding modulationorder is 4, and to be specific, Q=4 or Q_(m)=4), and 64 quadratureamplitude modulation (64QAM) (a corresponding modulation order is 6, andto be specific, Q=6 or Q_(m)=6). The code rates cover a relatively largerange, for example, a range ranging from 0.05 to 0.8. For example,because the eMBB service is characterized by a large amount oftransmitted data, a high transmission rate, and the like in datatransmission, the eMBB service has more modulation schemes, and coderates cover a larger range. Therefore, the mapping relationship set 2may be applicable to the eMBB service and the like supported by theterminal device. The eMBB service is merely an example. The mappingrelationship set 2 may also be applicable to more types of services, andan applicable service type may be specifically determined based on anactual application scenario. This is not limited herein.

Optionally, that the mapping relationship set described in thisembodiment of this application includes the mapping relationship set 1or the mapping relationship set 2 may be configured by the networkdevice. The network device may configure different mapping relationshipsets for the terminal device based on requirements of performanceindicators of different services supported by the terminal device, tomeet requirements of different performance indicators of differentservices of the terminal device. In specific implementation, if oneterminal device supports only one service, the network device mayconfigure one mapping relationship set for each of different terminaldevices that support different services. In other words, the networkdevice configures a plurality of mapping relationship sets for aplurality of terminal devices. In specific implementation, number ofmapping relationship sets may be determined by the network device, ormay be determined based on number of service types supported by theterminal device. This is not limited herein. The network device mayconfigure different mapping relationship sets for different services,and further, may deliver, based on a service carried on the terminaldevice, indication information of a mapping relationship setcorresponding to the service.

Optionally, that the mapping relationship set described in thisembodiment of this application includes the mapping relationship set 1or the mapping relationship set 2 may be preconfigured by the terminaldevice and does not need to be configured by the network device.Specifically, a definition manner of the mapping relationship set may bedetermined based on an actual application scenario. This is not limitedherein.

In a specific implementation, the network device configures differentmapping relationship sets for different services of the terminal device,or the terminal device pre-configures different mapping relationshipsets for different services of the terminal device, to better adapt tothe services of the terminal device. For example, because the URLLCservice has performance requirements of high reliability and low delay,modulation schemes of the URLLC service are mainly lower-ordermodulation schemes, and code rates are mainly concentrated in a low coderate range. A mapping relationship set (for example, the mappingrelationship set 1) of a modulation scheme and a code rate is speciallydefined for the URLLC service. On the one hand, a total number ofcombinations of the modulation scheme and the code rate can be reduced,so that overheads of downlink control information can be reduced whenthe terminal device is notified of the modulation scheme and the coderate. On the other hand, resolution in a low code rate working area canbe improved, to better adapt to a channel, and improve spectrumefficiency of the system.

Optionally, the network device may configure a default mappingrelationship set for the terminal device, or the terminal devicepre-configures a default mapping relationship set. The default mappingrelationship set is applicable to a requirement of a scenario ofreceiving a system broadcast message of the terminal device, forexample, an application requirement of receiving a system message(system information), receiving a paging message, receiving a randomaccess response, and the like. The default mapping relationship set isconfigured for the terminal device, so that a mapping relationship setrequired by a service of the terminal device is more complete, andservice resource configuration of the terminal device is more flexible.

Optionally, in some feasible implementations, the network device maydetermine the modulation scheme and the code rate based on informationsuch as a channel state or a to-be-scheduled resource. The networkdevice may determine, from the first mapping relationship set based onthe combination of the determined modulation scheme and code rate, theindication information corresponding to the combination of themodulation scheme and the code rate. The first mapping relationship setmay be a default mapping relationship set in a plurality of mappingrelationship sets. The indication information corresponding to thecombination of the modulation scheme and the code rate may be indexinformation such as an MCS index. Optionally, the first mappingrelationship set may also be a mapping relationship set corresponding toa service supported by the terminal device. For example, the servicesupported by the terminal device is the URLLC service. After the networkdevice determines the combination (set to the combination 1) of themodulation scheme QPSK (corresponding to the modulation order 2) and thecode rate 0.01, the network device may determine, from the mappingrelationship set 1 (Table 1), the indication information correspondingto the combination 1, that is, the MCS index is 0.

Optionally, the terminal device may report, to the network device, aservice type supported by the terminal device. The network device mayselect, from a plurality of mapping relationship sets based on theservice type supported by the terminal device, the first mappingrelationship set that is applicable to the service type supported by theterminal device. To be specific, the first mapping relationship set isone of the plurality of mapping relationship sets. For example, if theterminal device reports that the service type supported by the terminaldevice is URLLC, the network device may use, as the first mappingrelationship set, the mapping relationship set (the mapping relationshipset 1) shown in Table 1. The network device may determine a combinationof a modulation scheme and a code rate from the first mappingrelationship set based on information such as a channel state or ato-be-scheduled resource. The network device then determines indicationinformation corresponding to the combination of the modulation schemeand the code rate. For example, the network device determines themodulation scheme QPSK (corresponding to the modulation order 2) and thecode rate 0.01 based on information such as the channel state and theto-be-scheduled resource. Further, the network device may determine,from Table 1, that the indication information of the combination of themodulation scheme and the code rate is the MCS index that is equal to 0.

S22. The network device sends control information to a terminal device.

The control information may be specifically downlink control information(DCI). The DCI may include the indication information of the modulationscheme and the code rate, resource information of a data channel, andthe like. The indication information indicates an index of themodulation scheme and the code rate that are determined by the networkdevice. The resource information is used to determine number oftime-frequency resources.

The DCI sent by the network device to the terminal device may includemapping relationship set indication information. The mappingrelationship set indication information is used to indicate the firstmapping relationship set determined by the network device.

The DCI may include at least one bit that is used to indicate the firstmapping relationship set. For example, a mapping relationship set of amodulation scheme and a code rate that are used by the data channel isindicated in the DCI by using one bit. When a value of the bit is “0”,the mapping relationship set 1 (the mapping relationship set shown inTable 1) corresponds to the modulation scheme and the code rate that areused by the data channel. When the value of the bit is “1”, the mappingrelationship set 2 (the mapping relationship set shown in Table 2)corresponds to the modulation scheme and the code rate that are used bythe data channel. The terminal device may determine the first mappingrelationship set based on the value of the bit in the DCI.

Optionally, the network device delivers the DCI to the terminal device,and the terminal device may determine, based on a format of the DCI, amapping relationship set of a modulation scheme and a code rate that areused by the data channel corresponding to the DCI. The format of the DCIcorresponds to an original information bit included in the DCI. Forexample, a format 1 of the DCI corresponds to the mapping relationshipset 1 of the modulation scheme and the code rate that are used by thedata channel, and a format 2 of the DCI corresponds to the mappingrelationship set 2 of the modulation scheme and the code rate that areused by the data channel. The terminal device may determine the firstmapping relationship set based on the format of the DCI.

Optionally, the network device delivers the DCI to the terminal device,and the terminal device may determine, based on a type of informationcarried on the data channel, a mapping relationship set of a modulationscheme and a code rate that are used by the data channel correspondingto the DCI. For example, the terminal device may determine, by using theDCI, that the data channel carries a system message, and further, maydetermine the first mapping relationship set such as the default mappingrelationship set of the modulation scheme and the code rate that areused by the data channel.

If the DCI sent by the network device does not include indicationinformation of the first mapping relationship set, the terminal devicemay determine the default mapping relationship set as the first mappingrelationship set.

Before sending the DCI to the terminal device, the network device maysend configuration information to the terminal device, to indicate, byusing the configuration information, the first mapping relationship setof the modulation scheme and the code rate that are used by the datachannel corresponding to the DCI.

S24. The terminal device receives the control information, anddetermines a TBS configuration parameter based on the first mappingrelationship set and the control information.

The TBS configuration parameter may include the modulation scheme, thecode rate, and the number of time-frequency resources.

Specifically, after determining the first mapping relationship set, theterminal device may determine the modulation scheme and the code ratefrom the first mapping relationship set based on the indicationinformation (for example, an MCS index) that is of the combination ofthe modulation scheme and the code rate and that is included in the DCI.For example, if the terminal device determines that the first mappingrelationship set is the mapping relationship set 1 shown in Table 1, andthe MCS index indicated by the indication information is 0, the terminaldevice may determine the modulation scheme and the code rate fromTable 1. To be specific, the terminal device determines a modulationscheme 1 and the code rate 0.01 that are corresponding to thecombination 1 of the modulation scheme and the code rate.

The DCI may include the resource information of the data channel. Theresource information indicates time-frequency resources allocated by thenetwork device to the terminal device. The terminal device maydetermine, based on the time-frequency resources that are allocated bythe network device to the terminal device and that are indicated by theresource information and based on a fixed overhead time-frequencyresource, the number of time-frequency resources occupied by the datachannel. Specifically, the time-frequency resources occupied by the datachannel may be time-frequency resources available to the data channel,and may specifically include remaining time-frequency resources obtainedafter the fixed overhead time-frequency resource (a specifiedtime-frequency resource) is subtracted from the time-frequency resourcesallocated by the network device to the terminal device. The fixedoverhead time-frequency resource may include a time-frequency resourceoccupied by a demodulation reference signal (DMRS) corresponding to thedata channel, a time-frequency resource occupied by a channel stateinformation-reference signal (CSI-RS) sent by the network device, atime-frequency resource reserved by the network device, and the like.The time-frequency resource reserved by the network device may include atime-frequency resource occupied by a signal or a channel preconfiguredby the network device, for example, a time-frequency resource occupiedby a primary synchronization signal (PSS), a secondary synchronizationsignal (SSS), a physical broadcast channel (PBCH), or the like. Thetime-frequency resource reserved by the network device may also includea reserved time-frequency resource and the like dynamically notified bythe network device. Because the fixed overhead time-frequency resourcemay be in a unit of RE, the time-frequency resources occupied by thedata channel may also be in a unit of RE. In other words, a size of thetime-frequency resources occupied by the data channel may be less than asize of a physical resource block.

S26. The terminal device determines a TBS based on the modulationscheme, the code rate, and number of time-frequency resources.

In specific implementation, the TBS configuration parameter may furtherinclude number of transport layers that is supported by the data channelcorresponding to the DCI.

The terminal device may determine, based on precoding indicationinformation and the like included in the DCI, the number of transportlayers that is supported by the data channel corresponding to the DCI.

The terminal device may determine, based on a transmission modecorresponding to the data channel corresponding to the DCI, the numberof transport layers that is supported by the data channel.

Specifically, after determining the modulation scheme, the code rate,the number of time-frequency resources, and the number of transportlayers that is supported by the data channel, the terminal device maydetermine the TBS on the data channel.

The TBS may be a first TBS.

Optionally, the first TBS meets the following formula:

${{{First}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is number of time-frequency resources available to the data channel, vis the number of transport layers that is supported by the data channel,Q is a modulation order corresponding to the determined modulationscheme, and R is the determined code rate.

N may be quantized with a large granularity, and

${N = {K \times \left\lceil \frac{N\_ TEMP}{K} \right\rceil}},$K is a positive integer, where

N_TEMP may be the number of time-frequency resources available to thedata channel, N is quantized number of time-frequency resourcesavailable to the data channel, and N is used to calculate the first TBSand/or a second TBS. Details are not described below.

The first TBS may be obtained by looking up a table based on the numberN of time-frequency resources available to the data channel, the numberv of transport layers that is supported by the data channel, and themodulation scheme.

Number L of bits carried on a unit resource may be obtained by lookingup a table based on the modulation scheme and the number v of transportlayers that is supported by the data channel, and further, the first TBSis obtained by multiplying the number L of bits carried on the unitresource and a ratio of the number N of time-frequency resourcesavailable to the data channel to number of resources included in theunit resource.

Number L of bits carried in single layer transmission may be obtained bylooking up a table based on the number N of time-frequency resourcesavailable to the data channel and the modulation scheme, and further,the first TBS is obtained by multiplying the number L of bits carried insingle layer transmission and the number v of transport layers that issupported by the data channel.

Number L of bits carried in single layer transmission on a unit resourcemay be obtained by looking up a table based on the modulation scheme,and further, the first TBS is obtained by multiplying the number L ofbits carried in single layer transmission on the unit resource, a ratioof the number N of time-frequency resources available to the datachannel to a number of resources included in the unit resource, and thenumber v of transport layers that is supported by the data channel.

In some feasible implementations, the terminal device may determine asecond TBS based on parameters such as the modulation scheme, the coderate, the number of time-frequency resources, and the number oftransport layers that is supported by the data channel, and thendetermine the first TBS based on the second TBS. The second TBS may be atemporary TBS determined by the terminal device, and the terminal devicedetermines a finally required TBS, namely, the first TBS, based on thetemporary TBS and another parameter.

The another parameter may be a size of a Voice over Internet Protocol(VoIP) packet and/or a size of a Medium Access Control (MAC) controlelement (CE) packet.

The second TBS may meet the following formula:

${{{Second}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is number of time-frequency resources available to the data channel, vis the number of transport layers that is supported by the data channel,Q is a modulation order corresponding to the determined modulationscheme, and R is the determined code rate.

N may be quantized with a large granularity, and

${N = {K \times \left\lceil \frac{N\_ TEMP}{K} \right\rceil}},$K is a positive integer.

The second TBS may be obtained by looking up a table based on the numberN of time-frequency resources available to the data channel, the numberv of transport layers that is supported by the data channel, and themodulation scheme.

Number L of bits carried on a unit resource may be obtained by lookingup a table based on the modulation scheme and the number v of transportlayers that is supported by the data channel, and further, the secondTBS is obtained by multiplying the number L of bits carried on the unitresource and a ratio of the number N of time-frequency resourcesavailable to the data channel to number of resources included in theunit resource.

Number L of bits carried in single layer transmission may be obtained bylooking up a table based on the number N of time-frequency resourcesavailable to the data channel and the modulation scheme, and further,the second TBS is obtained by multiplying the number L of bits carriedin single layer transmission and the number v of transport layers thatis supported by the data channel.

Number L of bits carried in single layer transmission on a unit resourcemay be obtained by looking up a table based on the modulation scheme,and further, the second TBS is obtained by multiplying the number L ofbits carried in single layer transmission on the unit resource, a ratioof the number N of time-frequency resources available to the datachannel to number of resources included in the unit resource, and thenumber v of transport layers that is supported by the data channel.

The first TBS may be determined in any one of the following manners 1 to4.

Manner 1:

If the second TBS is greater than a first reference threshold, the firstTBS is equal to the second TBS. In other words, the second TBS may bedetermined as the first TBS, or the first TBS finally determined by theterminal device is equal to the second TBS.

Manner 2:

When the second TBS is less than or equal to a first referencethreshold, the first TBS is a first element in a first value set.

When the second TBS is less than or equal to the first referencethreshold, the first TBS may be an element that is in the first valueset and that is less than or equal to the second TBS, and an absolutevalue of a difference between the element and the second TBS is thesmallest.

If the second TBS is less than or equal to the reference threshold, thenetwork device may sequentially calculate differences between the secondTBS and elements included in the first value set, to obtain thedifferences between the second TBS and the elements included in thefirst value set. The network device may select an element that is in thefirst value set and that is less than or equal to the second TBS, wherean absolute value of a difference between the element and the second TBSis the smallest. The network device determines the element as the firstTBS. In this implementation, a value of the first TBS can preferentiallyensure data transmission reliability, and a transmission efficiency lossis the smallest.

For example, assuming that the second TBS is equal to 48, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined, bycalculating differences between the second TBS and elements in the firstvalue set, that an element 40 in the first value set is less than 48 andan absolute value of a difference between 40 and 48 is the smallest.Therefore, it may be determined that the first TBS is equal to 40.

For example, assuming that the second TBS is equal to 56, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined, bycalculating differences between the second TBS and elements in the firstvalue set, that an element 56 in the first value set is equal to thesecond TBS (which is equal to 56). Therefore, it may be determined thatthe first TBS is equal to 56.

The first TBS may be an element that is in the first value set and thatis greater than or equal to the second TBS, and an absolute value of adifference between the element and the second TBS is the smallest. Inthis implementation manner, a value of the first TBS can better meet aservice quality requirement when data transmission reliability slightlydecreases, and transmission efficiency is good.

For example, assuming that the second TBS is equal to 48, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe first TBS is equal to 56.

For example, assuming that the second TBS is equal to 56, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe first TBS is equal to 56.

Optionally, the first TBS is an element in the first value set, and anabsolute value of a difference between the element and the second TBS isthe smallest. If absolute values of differences between the second TBSand two elements are the same and are the smallest, a smaller element isselected. In this implementation, a value of the first TBS can minimizea deviation of data transmission reliability. Although transmissionefficiency slightly decreases, data transmission reliability isimproved.

Optionally, the first TBS is an element in the first value set, and anabsolute value of a difference between the element and the second TBS isthe smallest. If absolute values of differences between the second TBSand two elements are the same and are the smallest, a larger element isselected. In this implementation, a value of the first TBS can minimizea deviation of data transmission reliability. Although reliabilityslightly decreases, data transmission efficiency is improved.

For example, assuming that the second TBS is equal to 80, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe first TBS is equal to 72.

For example, assuming that the second TBS is equal to 48, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe first TBS is equal to 40.

Optionally, the first value set includes a size of a special datapacket, for example, the size of the VoIP packet and/or the size of theMAC CE packet.

As shown in the following set 1 or set 2, the first value set mayinclude only the size of the VoIP packet and/or the size of the MAC CEpacket.

Set 1: [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208, 224,256, 296, 328, 344, 392, 440, 488, 536].

Set 2: [8, 16, 24, 32, 40, 48, 56, 64, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536].

The first value set may also include a size of an enhanced voiceservices codec (EVS codec) packet.

For example, set 3: [8, 16, 24, 32, 40, 56, 72, 104, 120, 128, 144, 152,176, 208, 216, 224, 232, 256, 264, 296, 328, 336, 344, 392, 416, 424,440, 488, 512, 528, 536, 560, 632].

Set 4: [8, 16, 24, 32, 40, 48, 56, 64, 72, 104, 120, 128, 144, 152, 176,208, 216, 224, 232, 256, 264, 296, 328, 336, 344, 392, 416, 424, 440,488, 512, 528, 536, 560, 632].

As shown in the following set 5 or set 6, the first value set mayinclude the size of the VoIP packet and/or the size of the MAC CEpacket, and may include some elements inserted between elements with arelatively large difference in sizes of special data packets.

For example, set 5: [8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 136, 144,152, 176, 208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408,424, 440, 456, 472, 488, 504, 520, 536].

Compared with the set 1, elements 88, 136, 280, 288, 336, 376, 408, 424,456, 472, 504, and 520 in the set 5 are inserted elements. In thisembodiment of this application, some elements are inserted betweenelements with a relatively large difference in the sizes of the specialdata packets (the size of the VoIP packet, the size of the MAC CEpacket, the size of the EVS codec packet, and the like), so thatdifferences between elements in the first value set are evener. Thefirst TBS may be the size of the special data packet, or may be aninserted element, so that a value of the first TBS is more accurate andmore applicable.

Set 6: [8, 16, 24, 32, 40, 48, 56, 64, 72, 88, 104, 120, 136, 144, 152,176, 208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408, 424,440, 456, 472, 488, 504, 520, 536].

Compared with the set 2, elements 88, 136, 280, 288, 336, 376, 408, 424,456, 472, 504, and 520 in the set 6 are inserted elements.

As shown in the following set 7 or set 8, the first value set mayinclude the size of the VoIP packet, and/or the size of the MAC CEpacket, and/or the size of the EVS codec packet, and may include someelements inserted between elements with a relatively large difference insizes of special data packets.

Set 7: [8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 128, 136, 144, 152,176, 208, 216, 224, 232, 256, 264, 280, 296, 328, 336, 344, 392, 416,424, 440, 456, 488, 512, 528, 536, 560, 632].

Set 8: [8, 16, 24, 32, 40, 48, 56, 64, 72, 88, 104, 120, 128, 144, 152,176, 208, 216, 224, 232, 256, 264, 280, 296, 328, 336, 344, 392, 416,424, 440, 488, 512, 528, 536, 560, 632].

The first reference threshold is greater than or equal to a size of amaximum VoIP packet or a size of a maximum MAC CE packet. A value of thefirst reference threshold may be 536, 328, or the like.

Further, the first reference threshold is greater than or equal to asize of a maximum VoIP packet, a size of a maximum MAC CE packet, or asize of a maximum EVS codec packet. A value of the first referencethreshold may be 536, 328, 632, or the like.

In this embodiment of this application, according to a manner ofdetermining the first TBS by comparing the second TBS with the firstreference threshold, transmission of a small data packet (or referred toas a small-sized packet), especially transmission of a special datapacket, is more efficient. A manner of determining a TBS when a largedata packet is transmitted is more flexible, more applicable, and withbetter scalability. The special data packet may include the VoIP packet,the MAC CE packet, the EVS codec packet, and the like. This is notlimited herein.

Manner 3:

When an absolute value of a difference between the second TBS and asecond element in a first value set is less than or equal to a secondreference threshold, the first TBS is the second element in the firstvalue set.

After determining the second TBS, the terminal device may calculatedifferences between the second TBS and elements included in the firstvalue set, and obtain absolute values of the differences between thesecond TBS and the elements in the first value set. If an absolute valueof a difference between the second TBS and an element (set to the secondelement) in the first value set is less than or equal to the secondreference threshold, the element may be determined as the first TBS.

A value of the second reference threshold may be a predefined value. Thepredefined value may be 8, 16, or 32. The predefined value may be agreedon in a protocol or configured by the network device.

A value of the second reference threshold may be a product value of thesecond element and a predefined coefficient, for example, M times thesecond element, where M may be a decimal. The predefined coefficient maybe agreed on in a protocol or configured by the network device.

The predefined coefficient may be 0.01 or 0.1. Alternatively, thepredefined coefficient may be set to different values for differentsecond elements, and may be specifically determined based on an actualapplication scenario. For example, for a smaller second element, thepredefined coefficient may be a relatively small value, for example,0.01. For a larger second element, the predefined coefficient may be arelatively large value, for example, 0.05.

Manner 4:

When an absolute value of a difference between the second TBS and asecond element in a first value set is greater than a second referencethreshold, the second TBS is determined as the first TBS.

After determining the second TBS, the terminal device may calculatedifferences between the second TBS and elements included in the firstvalue set, and obtain absolute values of the differences between thesecond TBS and the elements in the first value set. If an absolute valueof a difference between the second TBS and an element (set to the secondelement) in the first value set is greater than the second referencethreshold, the second TBS may be determined as the first TBS.

The terminal device may determine the first TBS in different manners.When the absolute value of the difference between the second TBS and thesecond element in the first value set is greater than the secondreference threshold, the second TBS may be determined as the first TBS.Therefore, a manner of determining a TBS when a large data packet istransmitted is more flexible, more applicable, and with betterscalability. When the absolute value of the difference between thesecond TBS and the second element in the first value set is less than orequal to the second reference threshold, an element (the second element)in the first value set may be determined as the first TBS. An absolutevalue of a difference between the element and the second TBS is lessthan or equal to the second reference threshold. Therefore, transmissionof a small data packet (or referred to as a small-sized packet)especially transmission of a special data packet is more efficient.

S28. The network device determines a TBS based on the modulation scheme,the code rate, and number of time-frequency resources.

In a specific implementation, before determining the TBS on the datachannel, the network device may determine, based on a transmission modecorresponding to the data channel, number of transport layers that issupported by the data channel.

The network device may determine the TBS based on the modulation scheme,the code rate, the number of time-frequency resources, and the number oftransport layers that is supported by the data channel. The TBS may be afirst TBS.

The first TBS meets the following formula:

${{{First}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is number of time-frequency resources available to the data channel, vis the number of transport layers that is supported by the data channel,Q is a modulation order corresponding to the determined modulationscheme, and R is the determined code rate.

Specifically, the data channel may be a data channel sent by the networkdevice to the terminal device.

N may be quantized with a large granularity, and

${N = {K \times \left\lceil \frac{N\_ TEMP}{K} \right\rceil}},$K is a positive integer.

In some feasible implementations, the network device may determine asecond TBS based on parameters such as the modulation scheme, the coderate, the number of time-frequency resources, and the number oftransport layers that is supported by the data channel, and thendetermine the first TBS based on the second TBS. The second TBS may be atemporary TBS determined by the network device, and the network devicedetermines a finally required TBS, namely, the first TBS, based on thetemporary TBS and another parameter.

The another parameter may be a size of a VoIP packet and/or a size of aMAC CE packet.

The second TBS may meet the following formula:

${{{Second}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is number of time-frequency resources available to the data channel, vis the number of transport layers that is supported by the data channel,Q is a modulation order corresponding to the determined modulationscheme, and R is the determined code rate.

The first TBS may be determined in any one of the following manners 1 to4.

Manner 1:

If the second TBS is greater than a first reference threshold, the firstTBS is equal to the second TBS. In other words, the second TBS may bedetermined as the first TBS, or the first TBS finally determined by thenetwork device is equal to the second TBS.

Manner 2:

When the second TBS is less than or equal to a first referencethreshold, the first TBS is a first element in a first value set.

When the second TBS is less than or equal to the first referencethreshold, the first TBS may be an element that is in the first valueset and that is less than or equal to the second TBS, and an absolutevalue of a difference between the element and the second TBS is thesmallest.

If the second TBS is less than or equal to the reference threshold, thenetwork device may sequentially calculate differences between the secondTBS and elements included in the first value set, to obtain thedifferences between the second TBS and the elements included in thefirst value set. The network device may select an element from the firstvalue set and that is less than or equal to the second TBS, where anabsolute value of a difference between the element and the second TBS isthe smallest; and determine the element as the first TBS.

For example, assuming that the second TBS is equal to 48, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined, bycalculating differences between the second TBS and elements in the firstvalue set, that an element 40 in the first value set is less than 48 andan absolute value of a difference between 40 and 48 is the smallest.Therefore, it may be determined that the first TBS is equal to 40.

For example, assuming that the second TBS is equal to 56, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined, bycalculating differences between the second TBS and elements in the firstvalue set, that an element 56 in the first value set is equal to thesecond TBS (which is equal to 56). Therefore, it may be determined thatthe first TBS is 56.

The first TBS may be an element that is in the first value set and thatis greater than or equal to the second TBS, and an absolute value of adifference between the element and the second TBS is the smallest.

For example, assuming that the second TBS is equal to 48, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe first TBS is equal to 56.

For example, assuming that the second TBS is equal to 56, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe first TBS is equal to 56.

Optionally, the first TBS is an element in the first value set, and anabsolute value of a difference between the element and the second TBS isthe smallest. If absolute values of differences between the second TBSand two elements are the same and are the smallest, a smaller element isselected.

For example, assuming that the second TBS is equal to 80, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe TBS is equal to 72.

For example, assuming that the second TBS is equal to 48, and the firstvalue set is [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536], it may be determined thatthe TBS is equal to 40.

Optionally, the first value set includes a size of a special datapacket, for example, the size of the VoIP packet and/or the size of theMAC CE packet.

Optionally, as shown in the following set 1 or set 2, the first valueset may include only the size of the VoIP packet and/or the size of theMAC CE packet.

Set 1: [8, 16, 24, 32, 40, 56, 72, 104, 120, 144, 152, 176, 208, 224,256, 296, 328, 344, 392, 440, 488, 536].

Set 2: [8, 16, 24, 32, 40, 48, 56, 64, 72, 104, 120, 144, 152, 176, 208,224, 256, 296, 328, 344, 392, 440, 488, 536].

The first value set may also include a size of an EVS codec packet.

For example, set 3: [8, 16, 24, 32, 40, 56, 72, 104, 120, 128, 144, 152,176, 208, 216, 224, 232, 256, 264, 296, 328, 336, 344, 392, 416, 424,440, 488, 512, 528, 536, 560, 632].

Set 4: [8, 16, 24, 32, 40, 48, 56, 64, 72, 104, 120, 128, 144, 152, 176,208, 216, 224, 232, 256, 264, 296, 328, 336, 344, 392, 416, 424, 440,488, 512, 528, 536, 560, 632].

As shown in the following set 5 or set 6, the first value set mayinclude the size of the VoIP packet and/or the size of the MAC CEpacket, and may include some elements inserted between elements with arelatively large difference in sizes of special data packets.

Set 5: [8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 136, 144, 152, 176,208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408, 424, 440,456, 472, 488, 504, 520, 536].

Compared with the set 1, elements 88, 136, 280, 288, 336, 376, 408, 424,456, 472, 504, and 520 in the set 5 are inserted elements. In thisembodiment of this application, some elements are inserted betweenelements with a relatively large difference in the sizes of the specialdata packets (the size of the VoIP packet, the size of the MAC CEpacket, the size of the EVS codec packet, and the like), so thatdifferences between elements in the first value set are evener. Thefirst TBS may be the size of the special data packet, or may be aninserted element, so that a value of the first TBS is more accurate andmore applicable.

Set 6: [8, 16, 24, 32, 40, 48, 56, 64, 72, 88, 104, 120, 136, 144, 152,176, 208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408, 424,440, 456, 472, 488, 504, 520, 536].

Compared with the set 2, elements 88, 136, 280, 288, 336, 376, 408, 424,456, 472, 504, and 520 in the set 6 are inserted elements.

As shown in the following set 7 or set 8, the first value set mayinclude the size of the VoIP packet, and/or the size of the MAC CEpacket, and/or the size of the EVS codec packet, and may include someelements inserted between elements with a relatively large difference insizes of special data packets.

Set 7: [8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 128, 136, 144, 152,176, 208, 216, 224, 232, 256, 264, 280, 296, 328, 336, 344, 392, 416,424, 440, 456, 488, 512, 528, 536, 560, 632].

Set 8: [8, 16, 24, 32, 40, 48, 56, 64, 72, 88, 104, 120, 128, 144, 152,176, 208, 216, 224, 232, 256, 264, 280, 296, 328, 336, 344, 392, 416,424, 440, 488, 512, 528, 536, 560, 632].

The first reference threshold is greater than or equal to a size of amaximum VoIP packet or a size of a maximum MAC CE packet. Optionally, avalue of the first reference threshold may be 536, 328, or the like.

Further, the first reference threshold is greater than or equal to asize of a maximum VoIP packet, a size of a maximum MAC CE packet, or asize of a maximum EVS codes packet. Optionally, a value of the firstreference threshold may be 536, 328, 632, or the like.

In this embodiment of this application, according to a manner ofdetermining the first TBS by comparing the second TBS with the firstreference threshold, transmission of a small data packet (or referred toas a small-sized packet) especially transmission of a special datapacket is more efficient. Further, a manner of determining a TBS when alarge data packet is transmitted is more flexible, more applicable, andwith better scalability. The special data packet may include the VoIPpacket, the MAC CE packet, the EVS codec packet, and the like. This isnot limited herein.

Manner 3:

When an absolute value of a difference between the second TBS and asecond element in a first value set is less than or equal to a secondreference threshold, the first TBS is the second element in the firstvalue set.

After determining the second TBS, the network device may calculatedifferences between the second TBS and elements included in the firstvalue set, and obtain absolute values of the differences between thesecond TBS and the elements in the first value set. If an absolute valueof a difference between the second TBS and an element (set to the secondelement) in the first value set is less than or equal to the secondreference threshold, the element may be determined as the first TBS.

A value of the second reference threshold may be a predefined value. Thepredefined value may be 8, 16, or 32. The predefined value may be agreedon in a protocol or configured by the network device.

A value of the second reference threshold may be a product value of thesecond element and a predefined coefficient, for example, M times thesecond element, where M may be a decimal. The predefined coefficient maybe agreed on in a protocol or configured by the network device.

The predefined coefficient may be 0.01 or 0.1. Alternatively, thepredefined coefficient may be set to different values for differentsecond elements, and may be specifically determined based on an actualapplication scenario. For example, for a smaller second element, thepredefined coefficient may be a relatively small value, for example,0.01. For a larger second element, the predefined coefficient may be arelatively large value, for example, 0.05.

Manner 4:

When an absolute value of a difference between the second TBS and asecond element in a first value set is greater than a second referencethreshold, the second TBS is determined as the first TBS.

After determining the second TBS, the network device may calculatedifferences between the second TBS and elements included in the firstvalue set, and obtain absolute values of the differences between thesecond TBS and the elements in the first value set. If an absolute valueof a difference between the second TBS and an element (set to the secondelement) in the first value set is greater than or equal to the secondreference threshold, the second TBS may be determined as the first TBS.

The network device may determine the first TBS in different manners.When the absolute value of the difference between the second TBS and thesecond element in the first value set is greater than the secondreference threshold, the second TBS may be determined as the first TBS.Therefore, a manner of determining a TBS when a large data packet istransmitted is more flexible, more applicable, and with betterscalability. When the absolute value of the difference between thesecond TBS and the second element in the first value set is less than orequal to the second reference threshold, the element (the secondelement) in the first value set may be determined as the first TBS. Anabsolute value of a difference between the element and the second TBS isless than or equal to the second reference threshold. Therefore,transmission of a small data packet (or referred to as a small-sizedpacket), especially transmission of a special data packet, is moreefficient.

An operation performed in step S28 may be performed before step S22. Inother words, in a specific implementation, after determining themodulation scheme and the code rate, the network device may furtherdetermine the number of time-frequency resources and the number oftransport layers that is supported by the data channel, and determinethe first TBS based on the determined modulation scheme, code rate,number of time-frequency resources, and number of transport layers. Asequence of determining the first TBS and delivering the controlinformation is not limited, and may be specifically determined based onan actual application scenario.

S30. The network device sends, on the time-frequency resources, a datachannel based on a first TBS.

In specific implementation, for downlink data transmission, the networkdevice may send, on the time-frequency resources, the data channel basedon the determined first TBS. The time-frequency resources may betime-frequency resources actually occupied by the data channel.

S32. The terminal device decodes, based on the determined first TBS, thedata channel carried on the time-frequency resources.

In specific implementation, for downlink data receiving, the terminaldevice may decode, based on the determined first TBS, the data channelcarried on the time-frequency resources. The time-frequency resourcesmay be time-frequency resources actually occupied by the data channel.

Steps S30 and S32 may also be replaced with the following optional stepsS30′ and S32′.

S30′. The terminal device sends, on the time-frequency resources, a datachannel based on a determined first TBS.

S32′. The network device decodes, based on the first TBS, the datachannel carried on the time-frequency resources.

For uplink data transmission, the network device sends the DCI to theterminal device, and the terminal device may perform channel coding anddata modulation based on the determined modulation scheme and code rate.The terminal device may send, on the time-frequency resources actuallyoccupied by the data channel, the data channel based on the determinedfirst TBS.

For uplink data receiving, the network device may decode, based on thedetermined first TBS, the data channel carried on the time-frequencyresources actually occupied by the data channel.

By comparing some feasible manners of determining the TBS on the datachannel, it may be learned that the TBS meets the following formula:

${{TBS} = {8 \times \left\lceil \frac{N_{PRE} \cdot M_{RE}^{{DL},{PRB}} \cdot v \cdot Q_{m} \cdot R}{8} \right\rceil}},$where

N_(PRB) indicates number of physical resource blocks (PRB) allocated bythe network device to the terminal device, and N_(PRB) is indicated bythe DCI received by the terminal device. N_(RB) ^(DL,PRB) indicatesnumber of time-frequency resources available to the data channel in eachPRB, to be specific, remaining time-frequency resources obtained after afixed overhead time-frequency resource is subtracted in each PRB. EachPRB has same N_(RB) ^(DL,PRB) that is semi-statically configured by thenetwork device by using higher layer signaling; and v indicates thenumber of transport layers that is supported by the data channel, Q_(m)indicates the modulation order, and R indicates a target code rate (thecode rate) of the data channel. In an LTE system, N_(RB) ^(DL,PRB) is afixed value (120). In the foregoing implementation, N_(RB) ^(DL,PRB) maybe semi-statically configured by the network device, and a specificvalue of N_(RB) ^(DL,PRB) may be configured for different applicationscenarios.

However, in the 5G communication system, each PRB has different N_(RB)^(DL,PRB). In the foregoing implementation, a configuration manner ofN_(RB) ^(DL,PRB) is insufficiently flexible, cannot dynamically adapt toa specific application scenario, and as a result, cannot meetrequirements of performance indicators of different services of theterminal device. Consequently, spectrum efficiency of the system isreduced. In the foregoing implementation, all services supported by theterminal device use a same mapping table of an MCS and a code rate. Inother words, all the services use the same table of the code ratewithout distinction. Actually, different services have differentrequirements of performance indicators. For example, due to requirementsof URLLC for a delay and reliability, a main working area of URLLC is alow code rate area. Therefore, the low code rate area is required tohave a better granularity. In the foregoing implementation, MCSs used byall services are placed in one mapping table of an MCS and a code rate,and consequently, number of bits of the DCI may be increased, andapplicability is poor.

In this embodiment of this application, the terminal device maydetermine the modulation scheme and the code rate from the first mappingrelationship set based on the control information delivered by thenetwork device, and may further determine the number of time-frequencyresources based on the control information. The time-frequency resourcesare time-frequency resources for sending or receiving the data channel,to be specific, time-frequency resources actually occupied by the datachannel. Further, the terminal device may determine the TBS on the datachannel. In this way, the TBS determined based on the time-frequencyresources actually occupied by the data channel more matches the targetcode rate of the data channel, thereby improving accuracy of the TBS.The target code rate herein is a code rate that the network deviceexpects the data channel to reach, and the foregoing code rate is a coderate actually used by the data channel. The network device alsodetermines the TBS based on the same number of time-frequency resources,and therefore, the TBS determined by the network device also has theforegoing effect.

In addition, because the TBS is determined based on the modulationscheme, the code rate, and the number of time-frequency resources, arelatively accurate TBS can be determined in a same manner regardless ofnumber of scheduled resources and regardless of number of other overheadresources in the scheduled resources. Therefore, the manner ofdetermining a TBS is applicable to various scheduling scenarios, and themanner of determining a TBS is highly flexible and has good scalability.

Further, because the determined TBS is more accurate, number oftime-frequency resources allocated to the terminal device is notextremely small, so that a retransmission possibility can be reducedwhen sending the data channel or receiving the data channel, and thenumber of time-frequency resources allocated to the terminal device isnot extremely large either, thereby avoiding resource waste.

In this embodiment of this application, different mapping relationshiptables of modulation schemes and code rates may be configured forrequirements of performance indicators of services of different servicetypes of the terminal device. This can dynamically adapt to variousflexible resource allocation scenarios in the 5G communication system,operations are more flexible, and applicability is better. Further, inthe implementations provided in this embodiment of this application, amodulation scheme and a code rate may be directly determined based on aconfigured mapping relationship table of a modulation scheme and a coderate, and further, a TBS may be determined by using a predefined TBSdetermining formula without defining a TBS table and without operationsof searching a plurality of tables such as an MCS mapping table and aTBS table, so that implementation complexity of determining a TBS iseffectively reduced, data transmission efficiency and spectrumefficiency of the system are improved, and applicability is better.

FIG. 3 is a schematic structural diagram of a terminal device accordingto an embodiment of this application. The terminal device shown in FIG.3 may include a transceiver unit 31 and a processing unit 32. Each unitis described in detail below.

The transceiver unit 31 is configured to receive control informationsent by a network device. The control information includes indicationinformation and resource information of a data channel.

The processing unit 32 is configured to: determine a modulation schemeand a code rate based on a first mapping relationship set and theindication information received by the transceiver unit 31, anddetermine number of time-frequency resources based on the resourceinformation that is of the data channel and that is received by thetransceiver unit 31. The first mapping relationship set includes acorrespondence between the indication information and a combination ofthe modulation scheme and the code rate.

The processing unit 32 is further configured to determine a firsttransport block size (TBS) based on the modulation scheme, the coderate, and the number of time-frequency resources.

The transceiver unit 31 is further configured to: decode, based on thefirst TBS determined by the processing unit 32, the data channel carriedon the time-frequency resources, or send on the time-frequencyresources, the data channel based on the first TBS determined by theprocessing unit 32.

Optionally, a size of the time-frequency resources is less than a sizeof a physical resource block.

Optionally, the processing unit 32 is configured to:

determine the first TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers.

The first TBS meets the following formula:

${{{First}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is the number of time-frequency resources, v is the number oftransport layers that is supported by the data channel, Q is amodulation order corresponding to the modulation scheme, and R is thecode rate.

Optionally, the processing unit 32 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when the second TBS is greater than a first reference threshold, thefirst TBS is equal to the second TBS.

Optionally, the processing unit 32 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when the second TBS is less than or equal to a first referencethreshold, the first TBS is a first element in a first value set.

Optionally, the processing unit 32 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when an absolute value of a difference between the second TBS and asecond element in a first value set is less than or equal to a secondreference threshold, the first TBS is the second element in the firstvalue set.

Optionally, the processing unit 32 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when an absolute value of a difference between the second TBS and asecond element in a first value set is greater than a second referencethreshold, the first TBS is equal to the second TBS.

Optionally, the processing unit 32 is configured to:

determine the second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and the number of transportlayers.

The second TBS meets the following formula:

${{{Second}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is the number of time-frequency resources, v is the number oftransport layers that is supported by the data channel, Q is amodulation order corresponding to the modulation scheme, and R is thecode rate.

Optionally, the first reference threshold is greater than or equal to asize of a maximum VoIP packet or a size of a maximum MAC CE packet.

Optionally, the first element is an element that is in the first valueset and that is less than or equal to the second TBS, and an absolutevalue of a difference between the element and the second TBS is thesmallest.

Alternatively, the first element is an element that is in the firstvalue set and that is greater than or equal to the second TBS, and anabsolute value of a difference between the element and the second TBS isthe smallest.

Alternatively, the first element is an element in the first value set,and an absolute value of a difference between the element and the secondTBS is the smallest.

Optionally, the first value set includes at least one of a size of aVoIP packet and/or a size of a MAC CE packet.

Optionally, the first value set includes at least one of the followingvalues: 8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 136, 144, 152, 176,208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408, 424, 440,456, 472, 488, 504, 520, and 536.

Optionally, the second reference threshold is a predefined value, or thesecond reference threshold is a product value of the second element anda predefined coefficient.

Optionally, the processing unit 32 is configured to:

determine the number of time-frequency resources based on the resourceinformation received by the transceiver unit 31 and a specifiedtime-frequency resource, where the time-frequency resources includeremaining time-frequency resources obtained after the specifiedtime-frequency resource is subtracted from time-frequency resourcesindicated by the resource information.

The specified time-frequency resource includes one or more of atime-frequency resource occupied by a demodulation reference signal(DMRS) corresponding to the data channel, a time-frequency resourceoccupied by a channel state information-reference signal (CSI-RS) sentby the network device on the time-frequency resources indicated by theresource information, and a time-frequency resource reserved by thenetwork device.

Optionally, the first mapping relationship set is a default mappingrelationship set in a plurality of mapping relationship sets.

Alternatively, the transceiver unit 31 is further configured to receiveconfiguration information sent by the network device. The configurationinformation indicates the first mapping relationship set, and the firstmapping relationship set is one of a plurality of mapping relationshipsets.

Optionally, the control information further includes mappingrelationship set indication information, the mapping relationship setindication information indicates the first mapping relationship set, andthe first mapping relationship set is one of a plurality of mappingrelationship sets.

Optionally, a format of the control information indicates the firstmapping relationship set, and the first mapping relationship set is oneof a plurality of mapping relationship sets.

Alternatively, a type of information carried on the data channelindicated by the control information indicates the first mappingrelationship set, and the first mapping relationship set is one of aplurality of mapping relationship sets.

Optionally, the processing unit 32 is further configured to:

determine, based on precoding indication information included in thecontrol information, the number of transport layers that is supported bythe data channel.

Optionally, the processing unit 32 is further configured to:

determine, based on a transmission mode corresponding to the datachannel, the number of transport layers that is supported by the datachannel.

In specific implementation, the terminal device may execute, by usingunits in the terminal device, an implementation executed by the terminaldevice in the embodiment of FIG. 2. For a specific implementation, referto corresponding descriptions in the method embodiment shown in FIG. 2.Details are not described herein again.

FIG. 4 is a schematic structural diagram of a network device accordingto an embodiment of this application. The network device shown in FIG. 4may include a processing unit 41 and a transceiver unit 42. Each unit isdescribed in detail below.

The processing unit 41 is configured to: determine a modulation schemeand a code rate, and determine indication information based on a firstmapping relationship set and a combination of the modulation scheme andthe code rate. The first mapping relationship set includes acorrespondence between the indication information and the combination ofthe modulation scheme and the code rate.

The transceiver unit 42 is configured to send control information to aterminal device. The control information includes the indicationinformation determined by the processing unit 41 and resourceinformation of a data channel, and the resource information is used todetermine number of time-frequency resources.

The processing unit 41 is further configured to determine a firsttransport block size (TBS) based on the modulation scheme, the coderate, and the number of time-frequency resources.

The transceiver unit 42 is further configured to: decode, based on thefirst TBS, the data channel carried on the time-frequency resources, orsend on the time-frequency resources, the data channel based on thefirst TBS.

Optionally, a size of the time-frequency resources is less than a sizeof a physical resource block.

Optionally, the processing unit 41 is configured to:

determine the first TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers.

The first TBS meets the following formula:

${{{First}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is the number of time-frequency resources, v is the number oftransport layers that is supported by the data channel, Q is amodulation order corresponding to the modulation scheme, and R is thecode rate.

Optionally, the processing unit 41 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when the second TBS is greater than a first reference threshold, thefirst TBS is equal to the second TBS.

Optionally, the processing unit 41 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when the second TBS is less than or equal to a first referencethreshold, the first TBS is a first element in a first value set.

Optionally, the processing unit 41 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when an absolute value of a difference between the second TBS and asecond element in a first value set is less than or equal to a secondreference threshold, the first TBS is the second element in the firstvalue set.

Optionally, the processing unit 41 is configured to:

determine a second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and number of transport layers;and determine the first TBS based on the second TBS.

The first TBS meets the following condition:

when an absolute value of a difference between the second TBS and asecond element in a first value set is greater than a second referencethreshold, the first TBS is equal to the second TBS.

Optionally, the processing unit 41 is configured to:

determine the second TBS based on the modulation scheme, the code rate,the number of time-frequency resources, and the number of transportlayers.

The second TBS meets the following formula:

${{{Second}\mspace{14mu}{TBS}} = {8 \times \left\lceil \frac{N \cdot v \cdot Q \cdot R}{8} \right\rceil}},$where

N is the number of time-frequency resources, v is the number oftransport layers that is supported by the data channel, Q is amodulation order corresponding to the modulation scheme, and R is thecode rate.

Optionally, the first reference threshold is greater than or equal to asize of a maximum VoIP packet or a size of a maximum MAC CE packet.

Optionally, the first element is an element that is in the first valueset and that is less than or equal to the second TBS, and an absolutevalue of a difference between the element and the second TBS is thesmallest.

Alternatively, the first element is an element that is in the firstvalue set and that is greater than or equal to the second TBS, and anabsolute value of a difference between the element and the second TBS isthe smallest.

Alternatively, the first element is an element in the first value set,and an absolute value of a difference between the element and the secondTBS is the smallest.

Optionally, the first value set includes at least one of a size of aVoIP packet and/or a size of a MAC CE packet.

Optionally, the first value set includes at least one of the followingvalues: 8, 16, 24, 32, 40, 56, 72, 88, 104, 120, 136, 144, 152, 176,208, 224, 256, 280, 288, 296, 328, 336, 344, 376, 392, 408, 424, 440,456, 472, 488, 504, 520, and 536.

Optionally, the second reference threshold is a predefined value, or thesecond reference threshold is a product value of the second element anda predefined coefficient.

Optionally, the resource information indicates time-frequency resourcesallocated by the network device to the terminal device.

The number of time-frequency resources is number of remainingtime-frequency resources obtained after a specified time-frequencyresource is subtracted from the time-frequency resources indicated bythe resource information.

The specified time-frequency resource includes one or more of atime-frequency resource occupied by a demodulation reference signal(DMRS) corresponding to the data channel, a time-frequency resourceoccupied by a channel state information-reference signal (CSI-RS) sentby the network device, and a time-frequency resource reserved by thenetwork device.

Optionally, the first mapping relationship set is a default mappingrelationship set in a plurality of mapping relationship sets.

Alternatively, the transceiver unit 42 is further configured to sendconfiguration information to the terminal device, where theconfiguration information indicates the first mapping relationship set,and the first mapping relationship set is one of a plurality of mappingrelationship sets.

Optionally, the control information further includes mappingrelationship set indication information, the mapping relationship setindication information indicates the first mapping relationship set, andthe first mapping relationship set is one of a plurality of mappingrelationship sets.

Optionally, a format of the control information indicates the firstmapping relationship set, and the first mapping relationship set is oneof a plurality of mapping relationship sets.

Alternatively, a type of information carried on the data channelindicated by the control information indicates the first mappingrelationship set, and the first mapping relationship set is one of aplurality of mapping relationship sets.

Optionally, the control information includes precoding indicationinformation, and the precoding indication information indicates thenumber of transport layers that is supported by the data channel.

Optionally, the processing unit 41 is further configured to:

determine, based on a transmission mode corresponding to the datachannel, the number of transport layers that is supported by the datachannel.

In specific implementation, the network device may execute, by usingunits in the network device, an implementation executed by the networkdevice in the embodiment of FIG. 2. For a specific implementation, referto corresponding descriptions in the method embodiment shown in FIG. 2.Details are not described herein again.

FIG. 5 is a schematic structural diagram of a communication device 50according to an embodiment of this application. As shown in FIG. 5, thecommunication device 50 provided in this embodiment of this applicationincludes a processor 501, a memory 502, a transceiver 503, and a bussystem 504.

The processor 501, the memory 502, and the transceiver 503 are connectedby using the bus system 504.

The memory 502 is configured to store a program. Specifically, theprogram may include program code, and the program code includes acomputer operation instruction. The memory 502 includes but is notlimited to a random access memory (RAM), a read-only memory (ROM), anerasable programmable read only memory (EPROM), or a compact discread-only memory (CD-ROM). Only one memory is shown in FIG. 5.Certainly, a plurality of memories may be configured as required. Thememory 502 may be a memory in the processor 501. This is not limitedherein.

The memory 502 stores the following elements: an executable module or adata structure, or a subset thereof, or an extended set thereof:

an operation instruction, including various operation instructions andused for implementing various operations; and

an operating system, including various system programs and used toimplement various basic services and process a hardware-based task.

The processor 501 controls an operation of the communication device 50.The processor 501 may be one or more central processing units (CPU).When the processor 501 is one CPU, the CPU may be a single-core CPU, ormay be a multi-core CPU.

In specific application, components of the communication device 50 arecoupled together by using the bus system 504. In addition to a data bus,the bus system 504 may further include a power bus, a control bus, astatus signal bus, and the like. However, for clear description, varioustypes of buses in FIG. 5 are marked as the bus system 504. For ease ofillustration, FIG. 5 merely shows an example of the bus system 504.

FIG. 3 provided in the embodiments of this application, or the method ofthe terminal device disclosed in the foregoing embodiments, or FIG. 4provided in the embodiments of this application, or the method of thenetwork device disclosed in the foregoing embodiments may be applied tothe processor 501 or implemented by the processor 501. The processor 501may be an integrated circuit chip and has a signal processingcapability. In an implementation process, steps in the foregoing methodsmay be implemented by using a hardware integrated logical circuit in theprocessor 501, or by using instructions in a form of software. Theprocessor 501 may be a general purpose processor, a digital signalprocessor (DSP), an application-specific integrated circuit (ASIC), afield-programmable gate array (FPGA) or another programmable logicdevice, a discrete gate or transistor logic device, or a discretehardware component. The processor may implement or perform the methods,the steps, and logical block diagrams that are disclosed in theembodiments of this application. The general purpose processor may be amicroprocessor, or the processor may be any conventional processor orthe like. Steps of the methods disclosed with reference to theembodiments of this application may be directly performed andimplemented by using a hardware decoding processor, or may be performedand implemented by using a combination of hardware and software modulesin the decoding processor. A software module may be located in a maturestorage medium in the art, for example, a random access memory, a flashmemory, a read-only memory, a programmable read only memory, anelectrically erasable programmable memory, a register, or the like. Thestorage medium is located in the memory 502. The processor 501 readsinformation in the memory 502, and performs, in combination withhardware of the processor 501, the method steps of the terminal devicedescribed in FIG. 3 or the foregoing embodiments, or performs, incombination with hardware of the processor 501, the method steps of thenetwork device described in FIG. 4 or the foregoing embodiments.

All or some of the processes of the methods in the embodiments may beimplemented by a computer program instructing relevant hardware. Theprogram may be stored in a computer readable storage medium. When theprogram runs, the processes of the method embodiments are performed. Theforegoing storage medium includes any medium that can store programcode, such as a ROM, a random access memory RAM, a magnetic disk, or anoptical disc.

What is claimed is:
 1. A method for determining a transport block size(TBS) of a data channel, comprising: receiving, by a terminal device,control information from a network device, wherein the controlinformation comprises modulation indication information and resourceinformation of the data channel; determining, by the terminal device, amodulation order and a code rate according to a mapping relationship setand the modulation indication information, wherein the mappingrelationship set comprises a correspondence between the modulationindication information and a combination of the modulation order and thecode rate; determining, by the terminal device, number of time-frequencyresources according to the resource information; and determining, by theterminal device, the TBS according to the modulation order, the coderate, and the number of the time-frequency resources; wherein, accordingto the determined TBS, the terminal device decodes the data channelcarried on the time-frequency resources or sends the data channel on thetime-frequency resources; and wherein determining the TBS according tothe modulation order, the code rate, and the number of time-frequencyresources comprises: determining, by the terminal device, anintermediate TBS according to the modulation order, the code rate, thenumber of time-frequency resources, and number of transport layers; anddetermining, by the terminal device, the TBS according to theintermediate TBS; wherein when the intermediate TBS is less than orequal to a reference threshold, the TBS is determined to be an elementvalue in a value set.
 2. The method according to claim 1, wherein thevalue set comprises at least one of the following element values: 8, 16,24, 32, 40, 56, 72, 88, 104, 120, 136, 144, 152, 176, 208, 224, 256,280, 288, 296, 328, 336, 344, 376, 392, 408, 424, 440, 456, 472, 488,504, 520, and
 536. 3. The method according to claim 1, whereindetermining the number of time-frequency resources according to theresource information comprises: determining, by the terminal device, thenumber of time-frequency resources to be the number of time-frequencyresources indicated by the resource information subtracts number ofspecified time-frequency resources; wherein the specified time-frequencyresources comprise one or more of: a time-frequency resource occupied bya demodulation reference signal (DMRS) corresponding to the datachannel, a time-frequency resource occupied by a channel stateinformation-reference signal (CSI-RS) from the network device on thetime-frequency resources indicated by the resource information, and atime-frequency resource reserved by the network device.
 4. The methodaccording to claim 1, further comprising: before receiving the controlinformation from the network device, receiving, by the terminal device,configuration information from the network device, wherein theconfiguration information comprises the mapping relationship set, andthe mapping relationship set is one of a plurality of mappingrelationship sets.
 5. The method according to claim 1, wherein themodulation indication information comprises a modulation and codingscheme index (MCS index), wherein the mapping relationship set is acorrespondence between the MCS index, the modulation order and the coderate.
 6. The method according to claim 1, wherein the controlinformation further comprises precoding indication information, and themethod further comprises: before determining the TBS according to themodulation order, the code rate, and the number of time-frequencyresources, determining, by the terminal device according to theprecoding indication information, number of transport layers supportedby the data channel.
 7. A method for sending or receiving a datachannel, comprising: determining, by a network device, a modulationorder and a code rate of the data channel; determining, by the networkdevice, modulation indication information according to a mappingrelationship set and a combination of the modulation order and the coderate, wherein the mapping relationship set comprises a correspondencebetween the modulation indication information and a combination of themodulation order and the code rate; sending, by the network device,control information to a terminal device, wherein the controlinformation comprises the modulation indication information and resourceinformation of the data channel, and the resource information indicatesnumber of time-frequency resources; and determining, by the networkdevice, a transport block size (TBS) according to the modulation order,the code rate, and the number of time-frequency resources; wherein,according to the determined TB S, the network device decodes the datachannel carried on the time-frequency resources or sends the datachannel on the time-frequency resources; and wherein determining the TBSaccording to the modulation order, the code rate, and the number oftime-frequency resources comprises: determining, by the network device,an intermediate TBS according to the modulation order, the code rate,the number of time-frequency resources, and number of transport layers;and determining, by the network device, the TBS according to theintermediate TBS; wherein when the intermediate TBS is less than orequal to a reference threshold, the TBS is determined to be an elementvalue in a value set.
 8. The method according to claim 7, wherein thecontrol information instructs the terminal device to determine the TBSin transmitting or receiving the data channel on the time-frequencyresources.
 9. The method according to claim 7, wherein the value setcomprises at least one of the following element values: 8, 16, 24, 32,40, 56, 72, 88, 104, 120, 136, 144, 152, 176, 208, 224, 256, 280, 288,296, 328, 336, 344, 376, 392, 408, 424, 440, 456, 472, 488, 504, 520,and
 536. 10. The method according to claim 7, wherein the resourceinformation indicates time-frequency resources allocated by the networkdevice to the terminal device; wherein the number of time-frequencyresources is the number of time-frequency resources indicated by theresource information subtracts number of specified time-frequencyresources; and wherein the specified time-frequency resources compriseone or more of: a time-frequency resource occupied by a demodulationreference signal (DMRS) corresponding to the data channel, atime-frequency resource occupied by a channel stateinformation-reference signal (CSI-RS) from the network device, and atime-frequency resource reserved by the network device.
 11. The methodaccording to claim 7, further comprising: before sending the controlinformation to the terminal device, sending, by the network device,configuration information to the terminal device, wherein theconfiguration information comprises the mapping relationship set, andthe mapping relationship set is one of a plurality of mappingrelationship sets.
 12. The method according to claim 7, wherein themodulation indication information comprises a modulation and codingscheme index (MCS index), wherein the mapping relationship set is acorrespondence between a MCS index, a modulation order and a code rate.13. The method according to claim 7, wherein the control informationfurther comprises precoding indication information, and the precodingindication information indicates the number of transport layerssupported by the data channel.
 14. A terminal device, comprising: atransceiver and a processor; wherein the transceiver is configured to:receive control information from a network device, wherein the controlinformation comprises modulation indication information and resourceinformation of a data channel; and the processor is configured to:determine a modulation order and a code rate according to a mappingrelationship set and the modulation indication information wherein themapping relationship set comprises a correspondence between themodulation indication information and a combination of the modulationorder and the code rate; determine number of time-frequency resourcesaccording to the resource information; and determine a transport blocksize (TBS) according to the modulation order, the code rate, and thenumber of time-frequency resources; wherein, according to the determinedTBS, the terminal device decodes the data channel carried on thetime-frequency resources or sends the data channel on the time-frequencyresources; and wherein in determining the TBS according to themodulation order, the code rate, and the number of time-frequencyresources, the processor is configured to: determine an intermediate TBSaccording to the modulation order, the code rate, the number oftime-frequency resources, and number of transport layers; and determinethe TBS according to the intermediate TBS, wherein when the intermediateTBS is less than or equal to a reference threshold, the TBS isdetermined to be an element value in a value set.
 15. The terminaldevice according to claim 14, wherein the value set comprises at leastone of the following element values: 8, 16, 24, 32, 40, 56, 72, 88, 104,120, 136, 144, 152, 176, 208, 224, 256, 280, 288, 296, 328, 336, 344,376, 392, 408, 424, 440, 456, 472, 488, 504, 520, and
 536. 16. Theterminal device according to claim 14, wherein in determining the numberof time-frequency resources according to the resource information, theprocessor is configured to: determine the number of time-frequencyresources to be the number of time-frequency resources indicated by theresource information subtracts number of specified time-frequencyresources; wherein the specified time-frequency resources comprise oneor more of: a time-frequency resource occupied by a demodulationreference signal (DMRS) corresponding to the data channel, atime-frequency resource occupied by a channel stateinformation-reference signal (CSI-RS) from the network device on thetime-frequency resources indicated by the resource information, and atime-frequency resource reserved by the network device.
 17. The terminaldevice according to claim 14, wherein the transceiver is furtherconfigured to: before receiving the control information from the networkdevice, receive configuration information from the network device,wherein the configuration information comprises the mapping relationshipset, and the mapping relationship set is one of a plurality of mappingrelationship sets.
 18. The terminal device according to claim 14,wherein the modulation indication information comprises a modulation andcoding scheme index (MCS index), wherein the mapping relationship set isa correspondence between the MCS index, the modulation order and thecode rate.
 19. The terminal device according to claim 14, wherein thecontrol information further comprises precoding indication information,and wherein the processor is further configured to: before determiningthe TBS according to the modulation order, the code rate, and the numberof time-frequency resources, determine, according to the precodingindication information, number of transport layers supported by the datachannel.
 20. A network device, comprising: a processor and atransceiver; wherein the processor is configured to: determine amodulation order and a code rate of a date channel; and determinemodulation indication information according to a mapping relationshipset and a combination of the modulation order and the code rate, whereinthe mapping relationship set comprises a correspondence between themodulation indication information and a combination of the modulationorder and the code rate; the transceiver is configured to: send controlinformation to a terminal device, wherein the control informationcomprises the modulation indication information and resource informationof the data channel, and the resource information indicates number oftime-frequency resources; the processor is further configured to:determine a transport block size (TBS) according to the modulationorder, the code rate, and the number of time-frequency resources;wherein, according to the determined TB S, the network device decodesthe data channel carried on the time-frequency resources or sends thedata channel on the time-frequency resources; and wherein in determiningthe TBS according to the modulation order, the code rate, and the numberof time-frequency resources, the processor is configured to: determinean intermediate TBS according to the modulation order, the code rate,the number of time-frequency resources, and number of transport layers;and determine the TBS based on the intermediate TBS; wherein when theintermediate TBS is less than or equal to a reference threshold, the TBSis determined to be an element value in a value set.
 21. The networkdevice according to claim 20, wherein the control information instructsthe terminal device to determine a TBS in transmitting or receiving thedata channel on the time-frequency resources.
 22. The network deviceaccording to claim 21, wherein the value set comprises at least one ofthe following element values: 8, 16, 24, 32, 40, 56, 72, 88, 104, 120,136, 144, 152, 176, 208, 224, 256, 280, 288, 296, 328, 336, 344, 376,392, 408, 424, 440, 456, 472, 488, 504, 520, and
 536. 23. The networkdevice according to claim 20, wherein the resource information indicatestime-frequency resources allocated by the network device to the terminaldevice; wherein the number of time-frequency resources is the number oftime-frequency resources indicated by the resource information subtractsnumber of specified time-frequency resources; and wherein the specifiedtime-frequency resources comprise one or more of: a time-frequencyresource occupied by a demodulation reference signal (DMRS)corresponding to the data channel, a time-frequency resource occupied bya channel state information-reference signal (CSI-RS) from the networkdevice, and a time-frequency resource reserved by the network device.24. The network device according to claim 20, wherein the transceiver isfurther configured to: before sending the control information to theterminal device, send configuration information to the terminal device,wherein the configuration information comprises the mapping relationshipset, and the mapping relationship set is one of a plurality of mappingrelationship sets.
 25. The network device according to claim 20, whereinthe modulation indication information comprises a modulation and codingscheme index (MCS index), wherein the mapping relationship set is acorrespondence between a MCS index, a modulation order and a code rate.26. The network device according to claim 20, wherein the controlinformation further comprises precoding indication information, and theprecoding indication information indicates the number of transportlayers supported by the data channel.